This invention relates generally to a method and apparatus for parting thin-walled tubing, and more particularly concerns a method and apparatus for parting a segment from a moving length of shirred, thin-walled tubing.
In the manufacture and production of stuffed sausage products, the casing which holds and surrounds the product within is generally a thin-walled tubing which has a size to suit the product being formed. Particularly, the tubing for sausage and the like casings may vary from product to product, and manufacturer to manufacturer, but may be made of collagen, cellulosic, natural casing, and other commonly known and used materials. For efficiencies and economies of operation, many of these casings are stuffed with an emulsion at high speeds by various and known fitting or stuffing apparatuses. To be compatible with this apparatus capability, the sausage casings need be of sufficient length to handle the rapid injection of stuffing material with a minimal number of casing changes in order to make the operation more efficient.
It can be appreciated that long lengths of sausage casing present production and handling difficulties if attempts are made to stuff the same in the extended condition. Accordingly, the sausage stuffing industry, for instance, has employed a shirred sausage casing, one which is accordion pleated, gathered or folded so that, for example, a 50 foot (15.2 m.) length of tubing is compressed to a length of approximately 9 inches (23 cm.) or less.
Such a shortened sausage casing is easily stored and handled, quickly transferred to the stuffing apparatus during stuffing, and readily extended as the emulsion is forced within the inside of the tubing to unfold the pleats as it fills out the casing. In this sense, a shirred tubing or casing of finite or prescribed length (in the compressed state) is highly desirable for use in conjunction with high speed stuffing equipment.
Many apparatuses are known and available to produce this desirable shirred tubing, for example, the shirring machine as described in U.S. Pat. No. 3,315,300. Typically, a continuous length of thin-walled tubing is formed and provided to the mechanism which folds and pleats the material in the shirred condition. As the provided tubing is often and preferably continuous, provisions to sever the tubing into appropriate lengths for subsequent use on stuffing apparatuses are generally included in or with the apparatus which shirrs the tubing. In some instances, the tubing is severed into segments of appropriate length before or prior to the shirring of the tubing; thus, the severed segment itself is subsequently shirred. In other instances, the continuous length of tubing is shirred as it advances, and is severed into segments subsequent to the shirring step.
In U.S. Pat. No. 3,315,300, as referred to above, a continuous length of tubing is provided to a shirring mechanism, but the severing device is located in the apparatus at a position prior to the shirring mechanism. While the desirable shirred condition and prescribed length of shirred tubing are accomplished, it has been found that this type of cutting and shirring arrangement limits the speed at which the final shirred, segmented product is produced, with accordingly lower volume yield. This type apparatus does have the advantage, however, of enabling the cutting device therein to sever the tubing on a substantially flat or smooth surface so that the segmented lengths which are produced can be accurately predetermined.
Other apparatuses are known which provide a cutting device subsequent to or after the shirring step occurs. For instance, U.S. Pat. No. 3,942,221 discloses an apparatus for severing thin-walled tubing after the continuous length of tubing has passed through or across a shirring mechanism. In this apparatus, in order to cleanly sever the shirred tubing, means are provided to separate a portion of the shirred tubing to produce an unfolded area thereof. However, the advance of shirred tubing is restrained with each severed segment which is produced, since the moving continuous length is constrained by appropriate means during the entire cycle of separating and severing a portion of shirred tubing. In addition, this apparatus provides for the cutting device to score the periphery of the unfolded portion, and relies upon the tension of the moving segment to tear the scored tubing to achieve severance. This tearing may result in erratic lengths of some severed segments especially if the tubing has any flaws or weak spots therein. Moreover, the cutting device of the apparatus of this patent cuts the tubing at a plurality of points around its periphery to achieve the score for severing. Such point contact, however, may be non-uniform, with some points scoring deeper than others thereby producing a possibility for uneven and erratic tearing.
Another apparatus in which a shirred tubing is cut subsequent to the shirring step is disclosed in U.S. Pat. No. 3,112,517. In this patent the shirred continuous length of tubing is separated in a portion thereof while the tubing is continuously advancing; a holding finger, which moves along the support mandrel at the speed the tubing is being shirred, holds the shirred tubing in position. Another device, notably pinch rolls, advances the moving tubing more rapidly immediately ahead of the holding finger to separate the pleats of the shirred tubing to provide an unfolded portion between the pinch rolls and the holding finger. In the unfolded portion, while the holding finger and pinch rolls are still engaged in the tubing, a cutter scores the unfolded tubing at two points and initiates tears on opposite sides of the tubing, and as the pinch rolls continue to be moved, the unfolded portion is tensioned to complete the severing operation. Although the shirred tubing is allowed to move continually in an unrestrained movement during the separating and cutting cycles, the holding finger requires a specific mechanism to allow it to cyclically engage the moving tubing, move along with the tubing at the same rate thereof and then become disengaged from the tubing after the cutting step has been performed to return to its starting position at the end of the cycle.
Thus, while methods and apparatuses are known and available to sever segments of thin-walled tubing after a shirring operation has been performed thereon, it can be seen that there is room for further improvement in an apparatus of this type, and in the method of producing segments of shirred, thin-walled tubing.